Honestly the best way is to keep your eyes open, a lot of us are constantly reading eBay and other auction sites looking for gems. The other way is to read here, there's an eBay recommended thread in the vintage forum, and if Mike, Steve, or other respected vintage enthusiasts post a link there, chances are its a good one worth buying.

 

Reading Omegaforums.net is probably one of the best ways to find good Omegas for sale these days, between our for sale forum and the ebay listings that are discussed.